Current rectified signalling system



R. E. SMITH EI'AL CURRENT RECTIFIED SIGNALLING SYSTEM Sept. 22, 1959 2 Sheets-Sheet 1 Filed Oct. 3, 1955 R. E. SMITH, ETAL 2,905,102 CURRENT RECTIFIED SIGNALLING SYSTEM 2 Sheets-Sheet 2 asmgub a I ATTORNEY INVENTORS F u a m M 5 W L2 0 w k W L ,W

Sept. 22, 1959 Filed Oct. 5; 1955 United States Patent "CURRENT RECTIFIED SIGNALLING SYSTEM Raymond E. Smith and William R. Smith, Hamden, and John J. Baltrush, Jr., New Haven, Conn., assignors to The A. C. Gilbert Company, New Haven, Conn., a corporation of Maryland Application October 3, 1955, Serial No. 538,142

8 Claims. (Cl. 104-150) This invention relates to improvements in electrical systems for simulating the sound of a horn or whistle in the art of toys and particularly toy or model railroading. 'The present improvements specifically concern modifications of electrical systems for this purpose shown in a copending application of R. E. Smith, Serial No. 251,426, filed October 15, 1951, now US. Patent No. 2,791,972, granted May 14, 1957, and in another copending application by W. R. Smith, Serial No. 405,956, filed January 25, 1954, now US. Patent No. 2,792,409, granted May 14, 1957, both owned by the assignee of the present application.

An object of the present invention is to increase the intensity of horn or whistle imitating sound that can be produced by a very small size of dynamic loud speaker operating on electric power derived from a conventional source of current supply for toys.

Another object is to make possible the running of a toy train or other toy electrical load optionally or together with the production of a horn or whistle sound by means of unidirectional, vibrator interrupted, pulsating current as distinguished from the vibrator interrupted alternating current employed in the aforesaid copending application.

Another object and advantage of the invention of particular benefit in its use in toy electric railroading is the elimination of need for carrying a space consuming, stepby-step, eloctromagnetic switch on the toy train for reversing the direction of running of the propulsion motor in the locomotive. Such simplification becomes possible when unidirectional current, instead of alternating current, is supplied to the track because the direction of running of the train propulsion motor can then be reversed merely by changing the polarity of the unidirectional current that is fed to the two rails of the track.

Another object is to deliver constantly to a loud speaker, whether or not carried on a toy train, a fundamental wave form of unidirectional current pulsating, say, at twice the normal frequency of commercial alternating current, or at 120 cycles per second, to which wave form such speaker is operably nonresponsive and therefore remains silent, and then on desired occasion so to modulate said pulsating unidirectional current that the speaker is rendered active at will to generate a louder sound imitative of a horn or whistle than heretofore has been possible to a speaker of miniature size.

Another object is to increase the effectiveness of current pulsations that drive the air wave generating cone or diaphragm of the speaker by converting a 60-cycle alternating current to a 120-cycle pulsating unidirectional current by full-wave rectification, and then interrupting the l20-cycle fundamental wave form of pulsating uni- .directional current by the circuit making and breaking action of an electromagnetic vibrator operating to interrupt the speaker circuit at least 240 times per second.

A related object is to punctuate each loop of a fundamental pulsating unidirectional current wave of serrate :shape with a plurality of peak potentials occurring at 2,905,102 Patented Sept. 22, 1959 speaker operating frequency in contrast to normally much lower frequencies of the fundamental wave form that are incapable of inciting the speaker to audible sound generating action.

These and other objects of the invention will appear in greater particular from the following description of preferred embodiments of the improvements, which description has reference to the accompanying drawings wherein:

Fig; 1 shows diagrammatically one way of introducing a train carried current rectifier into the AC. system of electric connections disclosed in Fig. 10 of the aforesaid Patent No. 2,791,972 for practising the invention.

Fig. 2 shows the rectifier of Fig. 1 electrically connected diiferently in the system so as to be physically remote from the train.

Fig. 3 is like Fig. 1 showing how a difierent type of whistle sounding control switch may be connected in the system.

Fig. 4 shows how the whistle sounding control switch of Fig. 3 may be incorporated in the system of Fig. 2.

Fig. 5 shows an oscillogram of a wave shape of vibrator interrupted alternating current that is fed to the toy railroad track in Figs. 1 and 3 but that reaches only the rectifier in Figs. 2, 4 and 7.

Fig. 6 shows an oscillogram of a wave shape of unidirectional current that is fed to the track in Fig. 7.

Fig. 7 shows how a rectifier may be incorporated in the electrical system disclosed in the aforesaid application, Serial No. 405,95 6, to produce the whistle sounding wave shape shown in Fig. 6.

While the present improvements can be embodied in as great a variety of circuit arrangements and for as wide a range of uses as are mentioned in the aforesaid copending application, Serial No. 251,426, we have chosen herein as illustrative embodiments electrical systems wherein a full-wave, bridge type of rectifier 16 converts 60-cycle alternating current into lZO-cycle pulsating unidirectional current either for energizing a train-carried sound producer alone or for operating the train as well as energizing the sound producer. A non limiting practical rating for rectifier 16 may be 18 volts, /2 ampere. In the former instance the rectifier may be carried on the locomotive 13 or on some other car of a toy train together with an electromagnetic step switch of a type heretofore commonly employed for reversing the direction of travel of a train. But in the latter case the rectifier is stationed at the trackside apart from the train and may form part of the remote control system that conditions the electric current supplied to the track. In this arrangement the electromagnetic step switch can be eliminated and the train reversed merely by reversing the polarity of current delivered to the track rails.

In the drawings herein the toy train is represented graphically as a locomotive 13 carrying and driven by an electric propulsion motor 14 which may be of universal type such as will run on either alternating or direct current. The locomotive may be fashioned externally as shown in the aforesaid copending application to represent a diesel locomotive equipped with visible dummy signalling horns. Locomotive 13 carries concealed in its interior a signalling or sound producing device 18 whose details of construction may be as shown in the aforesaid copending patent application. The locomotive travels on relatively insulated, conductive, toy track rails 19. The electrical connections shown in Fig. 1 indicate that motor 14 derives its current supply through the track rails 19 in conventional manner by means of relatively insulated traction wheels on respectively opposite sides of the locomotive, and that the motor is controlled as to starting, stopping and reversal of its direction of running by the conventional electromagnetic relay or step switch 21 carried by the locomotive, as usual in toy trains impelled by alternating current. Fuller detatils of such step switch are set forth in the aforesaid copending patent application.

In Fig. 1 the source of electrical power for operating the entire system is represented as a conventional toy train controller 29 having three attachment terminals or binding posts 27, 43 and 45. Binding post 27 is in constant electrical connection with the manually operated voltage varying element 30 that takes off current from selective lengths of the train running section 28 of the secondary winding of a toy transformer in the controller 29. The controller is stationed at the trackside for manually governing the speed and direction of running of the train in the usual way. Post 45 is the base terminal of the controller. Post 27 will deliver from 7 /2 volts to 15 volts, while post 43 delivers only the maximum of, say, 15 volts. Speed of running of the train, in accordance with conventional practice, is under control of a manual turn button 01' handle which operates the current take-off contact arm 30 as shown in the aforesaid copending patent application. The primary winding 31 of the transformer derives power from any suitable source of alternating current (not shown) preferably at 60 cycles through an attachment cord 32.

The sound signalling device 18 is mounted on the interior of locomotive 13 and may take the form of a magnetic speaker either of the horn or cone type, but preferably is of the dynamic loud speaker type incorporating either a permanent type of field magnet or an electromagnetic field which latter is preferred in electrical systems for the particular purposes herein proposed. Details of such type of speaker are disclosed in the aforesaid copending patent application. Herein there is also shown a resistor 57 that may be carried on the interior of the locomotive and placed in electrical connection with the loud speaker in the relationship indicated. A capacitor or condenser 58 may also with advantage be added in shunt to resistor 57 as shown. Practical but non limiting electrical values for the resistor 57 and capacitor 58 and for other components of the electrical system are recommended in said copending application and are feasible in the system of Fig. 1 herein.

Herein also is shown a vibratory circuit making and breaking current interrupter 35 in which there is a resilient conductive reed 62 normally biased toward the right of the axis of the magnet core of the driving coil 36 so as normally to make circuit between the reed and a stationed contact 64. Another contact 65 is stationed on the opposite side of the reed and normally (when the reed is not vibrating) remains separated from electr'ical contact with the reedv Upon energizing the driving coil 36 with GO-cycle alternating current at the maximum voltage obtainable from controller terminals 45,43, the reed carried armature will be drawn toward the left at each half cycle of the alternating current; The reed will then separate from-contact 64 to break the circuit just before meeting contact 65 to remake the circuit. By this time the peak value of the alternating current in coil '36 has diminished to zero and reed armature 61 therefore becomes magnetically released so that the reed returns by its own spring bias to its starting position, whereupon contact 65 is opened and contact 64 becomes again closed. This excursion of the reed is repeated automatically at each half cycle of the uninterrupted alternating current by which the'driving coil 36 is incited. Thus in response to a 60-cycle alternating current the reed will make 120 excursions per second and at each such excursion the reed controlled circuit is broken twice. Thus there occur 240 breaks per second of the reed controlled or utilization circuit.

The hook-up shown in Fig. 1 enables the speaker 18 to be energized oper'atively at will in all train running conditions of the circuits so as to produce a whistle or horn imitating sound by merely closing a momentary "switch 38 to energize the normally deenergized reed driving coil 36 of the vibrator. The resulting interruptions of current flow to track rails 24, 25 impart to the wave form 69 of the fundamental alternating 60- cycle current in Fig. 5 a series of gap-s 70 bridged by peak potentials 71 forming a series of current impulses occurring at least twice as often as the frequency of excursions of the reed. Such gaps and peak potentials will be reflected in corresponding gaps and peak. potentials imposed on the fundamental serrated wave form of unidirectional current if the alternating current be rectified. Thus by the vibrator caused interruptions of alternating source current reflected in interruptions of unidirectional load current derived by rectification thereof there is imparted a corresponding rapidity of impulses to voice coil 54 and simultaneously to the field coil 50 of the electrodynamic loud speaker 18 to which impulses, when the current is rectified, the cone51 of the speaker responds with much greater amplitude and loudness of sound production than takes place in the purely alternating current systems of the aforesaid copending patent application. At other times, when the speaker is subject to only the uninterrupted fundamental wave of unidirectional current, its voice coil 54 is not incited with sufficient frequency and magnetic force to cause the speaker cone 51 to generate audible sound waves in the range of whistle or horn imitating tones.

For purposes of distinguishing between a relatively low frequency, as for instance the 60-cycle frequency of the fundamental wave form, and a relatively higher frequency, which may be a multiple of 60-cycle frequency, the fundamental wave frequency is herein sometimes referred to as a subsignalling frequency and the higher frequency of the interruptions imposed on the fundamental wave is referred to as a signalling frequency.

In Fig. 2 the full-wave rectifier 16 is shown apart from the rolling stock 13 and stationed at the trackside to form part of the remote control system that conditions the electric current supplied to the track. This enables rectified current to be delivered to the track and makes it possible to eliminate the electromagnetic step switch 21 from the locomotive or other rolling stock 13 thus making room for the whistle sounding means to be contained in cars of a smaller-gage railroad.

In the system of Fig. 2 the direction of train running is reversed by shifting the polarity reversing switch 41 which also is stationed apart from the track and rolling stock.

One contact 67 of reversing switch 41 is constantly fed with unidirectional current direct from rectifier 16 while the other reversing switch contact 68 is fed from the rectifier through the vibratory circuit interrupter 35 which may be constructed and operated like its counterpart in Fig. 1 when the whistle sounding switch 38 is closed. The circuit making and breaking function of vibrator 35 is normally out of action because the circuit that energizes its coil 36 is normally broken by the normally open momentary switch 38. But regardless of whether switch 38 is open or'is closed to sound the whistle, the polarity of'the track circuit is reversible by shifting the reversing switch 41.

As in Fig. 1, when and as long as as switch 38 remains normally closed, vibrator 35 will swing into action to modulate the direct current supplied to the track to cause the speaker 18 as in the aforedescrihed manner to emit its whistle or horn imitating sound. The reversiblemotor 14' operates as satisfactorily, and with sufiicient power, when switch 38 is closed as when it is open wherefore the sounding of the whistle has no discernible effect upon the speed or direction of running of the train and is independent of whether the train is standing idle or running in either direction.

In Fig. 3 a system is shown much likethat in Fig. 1 except that'the momentary on-and-off switch 38 is replaced by a double-throw switch 78 as a means of determining whether or not the vibratory circuit maker and breaker 35 shall function to modulate the alternating current delivered to the track in a manner to sound the whistle. However, in Fig. 3 the coil 36 of the vibrator is constantly energized and the reed 62 constantly vibrates regardless of the current shifting condition of switch 78. When switch 78 is conditioned as shown in Fig. 3 no whistle sounding interruption of the load or utilization circuit containing contacts 64 and 65 will occur because the reed is dead-ended at contact 79 of switch 78. When the switch 78 is shifted to throw contact 80 out of circuit and to establish contact 79 in circuit, current from the track can reach controller terminal 43 only through the circuit interrupting contacts 64, 65 in the vibrator which will have the same effect upon the electrical equipment carried by rolling stock 13 as occurs when switch 38 is closed in Fig. 1 to sound the whistle.

In Fig. 4, as in Fig. 2, the rectifier 16 is stationed re mote from the track and apart from the rolling stock 13 and feeds unidirectional current through whistle sounding switch 38 or 78 and through the polarity reversing switch 41 to the track and thence through the sound producing device 18.

It is to be understood that the load fed by the rectifier 16 directly, or optionally through the vibrator 35, need not be the propulsion motor of a toy train nor have any connection with a toy railroad, but may comprise the electric lighting or electrical animation of industrial toys representing such structures as factories, saw mills, fire houses, etc. commonly giving forth the sound of whistles, buzz saws, warning sirens, etc.

The diagrams of Figs. 1 to 4 will serve to illustrate how a rectifier such as 16 can be placed in proper electrical relation to comparable electrical elements in the systems of optionally usable sound control disclosed in a copending patent application of W. R. Smith, Serial No. 362,082, filed June 16, 1953, now U.S. Patent No. 2,826,996, granted March 18, 1958, owned by the assignee of the present application, while Fig. 7 illustrates the incorporation of such rectifier in the aforesaid Patent No. 2,792,409.

Referring specifically to Fig. 7, the elements of the system designated by the following reference numerals here inbefore referred to have the same relationship and function as in Figs. 1 to 6, inclusive, namely numbers 14, 18, 19, 21, 27, 28, 29, 30, 31, 32, 43, 45, 50, 51, 54, 57, 58. Still other elements of the system shown in Fig. 7 are electrically connected and function as they do in the afore said copending application, Serial No. 405,956, namely as follows:

In Fig. 7 a toy train is represented by rolling stock comprising a locomotive 13 hauling a sound car 12. The locomotive carries and is driven by the reversible propulsion motor 14 that is universal for alternating or direct current. The sound car 12 carries the whistle imitating sound producing device 18 hereinafter sometimes referred to as the sounder.

Motor 14 will operate on a fundamental direct current wave pulsating at 120 cycle frequency, hereinbefore referred to as signalling frequency, and also when the fundamental wave is subjected to momentary interruptions at frequencies which are multiples of 120 cycles such as 240 up to 720 times per second, herein sometimes referred to as signalling frequency.

Motor 14 on the locomotive 13 is controlled as to starting, stopping and reversal of the direction of train running by an electromagnetic relay or step switch 21 which may be carried by the sound car 12 and may operate as does the relay 21 in Figs. 1 and 3 except for being energized by pulsating direct current instead of by alternating current.

In the system of Fig. 7 the sounder 18 is caused to operate by the circuit conditioning effect of an electromagnetic vibratory circuit interrupter referred to herein as a vibrator 35. This vibrator incorporates reed motivated, make-and-break contacts that operate on principles that are in general explained in the copending patent applica= tion, Serial No. 251,426, aforesaid, to break up a fundamental 60 cycle alternating current wave, delivered by the power source 29, into higher frequency pulsations or peaks of potential that serve to vibrate diaphragm 51 of the sound producing device 18 at an audible range of frequency. This modifies the fundamental 60 cycle Wave form by introducing peak interruptions which may be made to occur with higher frequency than appears in the oscillogram of Fig. 5 depending upon the performance of the vibratory interrupter that is employed.

In the form of vibrator shown in Fig. 7 the free tip of vibratory reed 62 is provided with a magnetically attractable armature 61' and the reed is resiliently biased so that such armature is normally slightly toward the left of the common axis of the magnetic core 60 and its driving coil 36 so as normally to cause circuit making between a reed carried reed driving contact 37 and a stationed reed driving contact 39 that is constantly in electrical series with driving coil 36 through lead 40c. Circuit interrupting contacts 64 and 65 are resiliently stationed at opposite sides of the reed and both are normally separated respectively from contacts 63 and 63' carried by reed 62' when the latter is idle or not vibrating. Vibratory contacts 63 and 63' constantly have the same polarity as the reed 62 itself which is made of conductive metal.

All of the circuits shown in Fig. 7 are not energized or alive at the same time but are energized or deenergized sequentially and in groups at any given time depending on the circuit controlling condition of a manually actuated, whistle sounding switch designated 38' as a whole in Fig. 7. Switch 38' has a single actuating handle 92 that swings on a pivot 91.

The whistle sounding switch 38 in Fig. 7 comprises four conductive spring leaf contacts '81, 82, 83, 84. The left ends of these contact leaves are relatively insulated and fixedly stationed. The resilience of the contact leaves normally biases them into their relative positions shown in Fig. 7. Contacts 82 and 83 are prevented from ever touching each other by intervening insulation 88. Suificient depression or downward flexing of the free end of contact 81 will, with lag, cause depression of contact 84 by thrusting downward on the insulative coupling 89.

Depression or downward flexing of resilient contact leaf 81 is accomplished by the swinging cam action of an insulative boot '90 on handle 92 turning counter clockwise about pivot 91. The counter clockwise sweep of cam about its pivot 91 with the switch handle 92 takes place against the constant pull of a return spring (not shown) and handle 92 carries a conductive arm 93 that wipes along a coil of bared, individually insulated convolutions of resistance wire 94 thus performing as a variable rheostat. In the positions of parts shown in Fig. 7 arm 93 is separated from conductive contact with resistance coil 94 when swung to its normal or extreme position toward the right. In other positions of handle 92 arm 93 wipes conductively along the resistance coil 94 as aforesaid.

Also in the system of Fig. 7 a booster transformer 95 has a primary winding 96 powered at 15 volts from the current supply terminal 43 and capable of inducing current simultaneously in two, back-to-back, secondary windings 72 and 73. Secondary winding 72 derives from primary winding 96 an induced voltage substantially equal to that impressed upon the primary winding. Secondary coil 73 derives from primary winding 71 an induced voltage equal to only substantially half of that impressed upon the primary winding. The current induced in the fullvoltage secondary winding 72 acts through coil 36 solely to drive the reed 62' of the vibrator. The current induced in half-voltage secondary winding 73 acts through a circuit traced through contacts 64 or 65, and conductors 66, 25, 27, 30, 28, 42, 45, 23, 97, 25', 57 and 73 to augment the current derived at 7 /2 to 15 volts from the takeoh? arm 31), in the power source 29. These two sec- Ql dlr es of the booster transformer. thus helpinsure that the intermittent electrical im pulses delivered through a full-wave rectifier 97 to the track rails 19 19" by the ac tion of -the vibrator 35" shall carry enough power to sound the whistle with sufficient loudness and a desirablechara'cteristic of tone while the train is being run at any of its possible speeds as well as while the train is standing still. They also insure that the sounding of the whistle shall havejno appreciable effect upon the usual speed and ,performance of the train responsive to shifting of position of the controller handle 30. i

For convenience in comparing the interrupted wave shape of alternating current in Fig. with the interrupted wave shape of unidirectional current in Fig. 6, it'is explained that the four interruptions of each cycle of alternating current at 70 in Fig. 5 are the natural result of the 60 cycle frequency impartedto reed 62 in the vibrator 35 (of Figs. 1 to 4) operating as aforesaid, whereas the presence of the driving contacts 37 and 39 in vibrator 35 (of Fig. 7) enables the periodicity of reed vibration to be increased by varying mechanically the resonance of the reed '62 and/or the magnetic force of its driving coil 36. Such variation is capable of producing, for instance, six interruptions'at 70 in each rise and fall of'the rectified current, 'or twelve interruptions in the two such rises and falls that correspond to one cycle of the alternating current supplied to the rectifier 97. Hence as shown in Fig. 6 the frequency of interruptivepulses of rectified 60 cycle alternating current that reaches the track rails in Fig. 7 may be as high as 12 times 60 or 720 impulses per second in Fig.7. B represents the zero voltage or graph base line in both Figs. 5 and 6. The inductive peak 71' that accompanies each gap 270' in Fig.6 is greatly augmented by the power of the booster transformer 95 in the system of Fig. 7 wherefore'a louder whistle sound and less disturbance of propelling power in the train motor 14 results from use of an alternating current source that is stepped down to notover 15 volts.

The appended claims are directed to and intended to cover not only the specific hook-up of circuits and particular combination ofelectrical elements herein disclosed to illustrate the invention, but also all modifications and variations thereof that come within the principles'of cooperative electrical action that newly characterizes'the invention as defined by the claims. i

'We claim:

-1. The method of causing at will an occasional emission of whistle imitating sound from a nonnally silent sound producingdevice of the electromagnetic type having a vibratory air wave inducer constantly sensitive to electric current supplied to said device, which comprises, regularly energizing said device through a utilization circuit carrying a flow of unidirectional current pulsating at subsignalling frequency and having a fundamental looped wave shape of constant polarity in response to which said inducer will vibrate at said frequency whereby said air wave inducer is not incited to vibrate with sufiicient rapidity and amplitude to generate a whistle imitating sound, and on occasion intermittently making and breaking said utilization circuit in a manner to cause a plurality of complete gaps in each loop of said wave shape bridged by peaks of potential occurring at signalling frequency andintensity, whereby said air wave inducer is incited by unidirectional current alone to vibrate with sulficiently great rapidity and amplitude to generatea whistle imitating sound. i

2. The method of causing at will by remoteelectrical control the sounding of a whistle-like tone by anorinally silent sound producing device of the electromagnetic type havinga magnetically impulsed vibratoryair wave inducer carried on the rolling stock of a toy electric train running on toy track rails and impelled by a train carried propulsion motor electrically energized by current conducted through said rails, which comprises, regularly n izi sa d. n q u sien meter from a upp y of al erhating" current of simple sinusoidal wave shape derived through said track rails at'frequency afiording train'im-j pelling energization of said impulsion motor, supplying to utilization circuit repeatedly with" sufiicient rapidity to cause a plurality of complete gaps in each loop of said fundamental wave shape of said rectified current bridged by peak potentials occurring at signalling frequency, thereby to incitesjaid'inducer to vibrate with suflicient rapidity and amplitude to generate an audible hoirn like Q I l 3. An electrical system comprising, an electromagnetic sound signalling device adapted td'reIiiainSiIentwhen subjected to current impulses" occurring 'at'subsignalling frequency; 'acurrent transla;tivehhductive loadfa source of continuous current alternating at s'ubsignalling 'frequency,'a vibratory circuitriiakerand breaker including an electromagnet energized by said 'alternatingcurirnt, a reed operably responsive to said electromagnet in a nn to p orm i ato 'sw t n i oa' c i ata i i a 'd' a 's nall nsidsv set sqma t in said load circuit arranged to be "opened and closed momentarily by said reed a sufficient number'of times during each vibratory eXcursion'ofsaid reed to. break said load circuit with signalling frequency, a rectifier in series with said vibrator c ontacts connected to derive alternating current from said source, a signal.sonnding circuit containing sound signallingdevice and connected to derive pulsating unidirectional current from said rectifier, and means selectively to render said vib natory current maker and breaker actiye or inactive for controlling the m sion o .s t by id s alli de e '4- A el c i a s tem com ises to rac rails, t train rolling ,stockonsaid rails, a cur'rent translative indu v l adca ried y saidfrol e Stock, Q I s Q continu u ur ent alterna i at i b sna n fre u n y, a vibratory circuit maker and breaker including an electromag en r zedh id al e a in t entw th a re d ope y resp n ve tosa d e ee romagn is? ete to perform vibratory excursions, a load circuit containing said inductive load, electric contacts in said load circuit arranged to be opened and closed momentarilyby said r e .a .suflficient number of. t me .dur n eachlvibratq excursion of said reed to break said load circuitwith signalling frequency, a rectifier in said load circuit in series 'with said vibrator contacts connected toderive alternating currentltherethrough from said source, an electroniagnetic sound signalling 'device carried by said rolling stock and connected in said'load circuit. to derive pulsating unidirectional current from 'said rectifier, and means selectively to render said vibratory current maker and breaker active or inactivefor controlling the emission of sound bysaid signalling device.

5. An electrical system comprising, an electromagnetic sound signalling device adapted to remain silent when subjectedto c urrentdmpulses occurringat subsignallin'g frequency, a translative inductive load, a source 'of continuous current alternating at subsignallyin'g trc'quency, a vibratory circuit maker and breaker including an electromagnet energizedby a solenoidderiving alternating current from said source, a reed responsive to said electromagnet in a manne'r to perform vibratory excursions, reed motivated'reed driving contacts in series with said solenoid wherefore to increase the frequency of said vibratory excursions of said, reed, a load circuit, electric contacts insaid load circuit arranged to be' opened and closed momentarilyby said excursions of said reeda sufficient number of times duringeach vibratory excursionof said Ic PEQK fiaid load circuit with signalling'frequency,

a rectifier in said load circuit connected to deliver pulsating unidirectional current to said sound signalling device, and means to vary and determine the strength of current delivered to said solenoid wherefore to vary and determine the tone and intensity of sound emitted by said signalling device.

6. An electrical system comprising, toy track rails, toy rolling stock on said rails, an electric utilization circuit including said rails and rolling stock, a rectifier in said circuit, a source of alternating current delivered to said rectifier at subsignalling frequency, a train propulsion motor in said circuit, a sound signalling device connected in said circuit to derive from said rectifier unidirectional current pulsating with a fundamental wave [form of subsignalling frequency and operative to produce sound only when energized by current impulses of signalling frequency, a vibratory circuit maker and breaker operative when switched into said circuit to impose peak potentials of signalling frequency on said fundamental wave form of said unidirectional current, a booster transformer electrically powered from said source and electrically connected to assist in energizing said circuit maker and breaker, an electric switch in stationary relation to said rails electrically connected in a first condition to exclude said circuit maker and breaker and said booster transformer from said circuit and in a second condition to include said circuit maker and breaker and said booster transformer in said circuit, thereby to cause said device to produce signalling sound only in said second condition of said switch.

7. An electrical system as defined in claim 6, together with a variable rheostat electrically connected to modulate the energizing of the said circuit maker and breaker by the said booster transformer.

8. An electrical system as defined in claim 7, together with a single manually operable handle arranged mechanically to actuate both the said current switching means andthe said variable rheostat in predetermined sequence.

References Cited in the file of this patent UNITED STATES PATENTS 2,521,240 Milne Sept. 5, 1950 2,714,859 Klemme Aug. 9, 1955 2,791,972 Smith May 14, 1957 2,792,409 Smith May 14, 1957 

